Comparative phytochemical and morphological analyses of three Italian Primula species.

The taxonomy of alpine Primula species has long been in dispute because of high morphologic variability and several hybridisations. In Primula species, the trichome height and the colour of hair-tips are usually indicated as diacritic characters, but in our experience this is not adequate. The present study, focused on Primula auricula, Primula daonensis and Primula hirsuta, therefore proposes the use of other morphologic trichome parameters (size and dimensional ratio of stalk, neck and gland head). Phytochemical investigations about the flavonoid composition (epicuticular and vacuolar) of leaves, as taxonomic markers, have also been performed. We report the isolation and identification of two new flavonol glycosides, isorhamnetin 3-O-(2,6-di-O-beta-D-glucopyranosyl-beta-D-glucopyranoside) (1) and kaempferol 3-O-(2-O-alpha-L-rhamnopyranosyl-6-O-beta-D-xylopyranosyl-beta-D-glucopyranoside) (2) and of eight known flavonoids. Size and dimensional ratio of the three trichome elements (stalk, neck and glandular head) are typical for each species analysed. The flavonoid profile well characterise the entities under study. Three different profiles have been obtained with both vacuolar and epicuticular flavonoids. The morphologic and phytochemical markers proposed in this work seem to be parameters which significatively discriminate the species under study.

Analysis of late stage flower development in Primula vulgaris reveals novel differences in cell morphology and temporal aspects of floral heteromorphy.

Heterostyly in Primula is characterized by the development of long-styled pin and short-styled thrum flowers, with anthers midway down the corolla tube in pin flowers, and at its mouth in thrum flowers. Other differences include pollen size and stigmatic papillae length. Several linked genes at the S locus control these differences. In this study we have analyzed pin and thrum flowers through the temporal development of heteromorphy.These studies indicate that the S locus linked genes that orchestrate heteromorphic flower development act in coordination, but with different temporal and spatial dynamics. Style length is differentiated by longer style cells in pin than thrum. However, our studies on cell shape and size within the corolla tube show that a different mechanism mediates the dissimilar elevation of anthers between pin and thrum types. These studies have also revealed that upper corolla tube cells in thrum flowers are wider than those in pin flowers. This results in a larger corolla tube mouth in thrum flowers and represents a new and previously undocumented heteromorphic variation between pin and thrum flowers.

A comparison of early floral ontogeny in wild-type and floral homeotic mutant phenotypes of Primula.

Primula flowers are heteromorphic with individual plants producing either pin-form or thrum-form flowers. We have used scanning electron microscopy to observe early development of wild-type flowers of primrose (Primula vulgaris), cowslip (P. veris), and the polyanthus hybrid (P. x tommasinii x P. vulgaris). Floral ontogeny in Primula is different from that observed in the well-studied models Antirrhinum majus and Arabidopsis thaliana and our studies reveal morphological landmark events that define the sequence of early floral development in Primula into specific stages. Pin-form and thrum-form flowers are indistinguishable during early development with differentiation of the two floral morphs occurring beyond the differentiation of floral organs. Early ontogeny of flowers with homeotic mutant phenotypes was also studied to determine the timing of developmental reprogramming in these mutants. Phenotypes studied included Hose in Hose and Jack in the Green that develop petaloid sepals and leafy sepals, respectively, and Jackanapes plants that carry both these dominant mutations. Recessive double and semi- double flowers that produce additional whorls of petals and/or stamens in place of carpels were also studied. We describe a previously undocumented recessive Primula mutant phenotype, sepaloid, that produces sepals in place of petals and stamens, and a new non-homeotic, dominant mutant phenotype Split Perianth, in which sepals and petals fail to fuse to form the typical calyx and corolla structures. The molecular basis of these mutant phenotypes in relation to the ABC model is discussed.